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  • PRIMARY DEFENCES: prevent pathogens from entering the body
    • SKIN
      • outer layer called EPIDERMIS
        • most cells of epidermis are KERATINOCYTES
          • produced by mitosis at base of epidermis which migrate out to surface of skin
            • as they migrate, the dry out and cytoplasm is replaced by KERATIN. this is called KERATINISATION
              • takes about 30 days
              • by the time the cells reach surface, they are dead. this acts as the effective barrier to pathogens
      • food and air from environment may harbour many microorganisms, so airways and lungs and digestive systems are protected.
        • Epithelial layer contains GOBLET CELLS
          • mucus traps pathogens
        • Epithelium also has ciliated cells
          • waft away mucus to top of trachea to be swallowed and passed down to digestive system
            • stomach acidity (low pH) denatures pathogens enzymes and kills
              • mucus traps pathogens
      • Is also in
        • gut
        • genital areas
        • anus
        • ears
        • nose
    • EYES
      • antibodies in tear fluid
      • wax traps pathogens
    • VAGINA
      • Maintains relatively acidic conditiond


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